Known switching devices are designed to allow the correct operation of specific parts of the electric circuits in which they are installed, and of the operators of such electric circuits.
Circuit breakers are known switching devices which perform a protective function against failures occurring in the associated electric circuit. For example, a circuit breaker can be actuated, during its operation, between a closed position, where it allows a current flowing between two parts of the associated electric circuit, and an open position where it interrupts such current flow. Thus, the circuit breakers can be suitable for interrupting fault currents, e.g. an overload or short-circuit current.
Disconnectors are known switching devices which perform a disconnecting function between two parts of the associated electric circuit, to ensure the safety of the operators working on one of the two disconnected parts. A disconnector can be actuated, during its operation, between a connection position, where an electrical connection between the two parts is realized by the disconnector itself, and a disconnection position, where the two parts are physically separated by the disconnector itself in order to interrupt their electrical connection.
As the circuit breaker, the disconnector in the connection position can withstand the flowing therethrough of fault currents but, contrary to the circuit breaker, it cannot be actuated to interrupt such fault currents. Hence, a circuit breaker and a disconnector can be associated in each phase of an electric circuit, and can be connected in series to perform the current interruption functionality between two parts of the electric circuit and the disconnection functionality between such two parts, respectively.
Under normal operation conditions, a current flows between the two parts of the electric circuit through the current path realized by the circuit breaker in the closed position and the disconnector in the connection position. The disconnector can be actuated from the connection to the disconnection position only after that the circuit breaker has been actuated from the closed to the open position.
The circuit breakers and the associated disconnectors are installed in an electric unit, such as a switchgear. The electric unit includes a distribution compartment containing power distribution means, e.g. distribution bars, and a load compartment containing cables (or other connection means) connected to one or more electric loads.
The distribution means and the corresponding one or more electric loads are operatively electrically connected through the circuit breakers and the associated disconnectors. For example, the circuit breakers and the disconnectors are located into the electric unit between the distribution and load compartments.
In some applications a metal earthed segregation between the distribution and load compartments is specified.
The circuit breakers and the associated disconnectors are conceived as separated devices, e.g., each having an own casing occupying a dedicated space, or comportment, into the electric unit. In this case, further internal space of the electric unit has to be occupied by connection means provided for electrically connecting the associated circuit breakers and disconnectors (placed at difference locations into the electric unit).
In this example the above mentioned metal earthed segregation can be fulfilled by making the casing of the disconnectors entirely of metal material.
European patent application EP1928065 discloses a disconnector unit having a casing defined by coupling a first insulating shell and a second metal shell, wherein the metal earthed segregation is fulfilled by the metal shell.
In other known solutions, the associated circuit breakers and disconnectors are housed into the same casing, or tank, which is entirely made of metal material in order to provide the metal earthed segregation.
At the current state of the art, although known solutions perform in a rather satisfying way, there is still reason and desire for further improvements.
Exemplary embodiments described herein provide an electric switching device for an electric circuit, having at least an electric phase that includes at least a circuit breaking unit associated with a disconnector unit, wherein the circuit breaker unit has at least a circuit breaker movable contact which can be actuated, during the operation of the circuit breaker unit, between a closed position where it is electrically coupled to a corresponding circuit breaker fixed contact and an open position where it is electrically separated from the corresponding circuit breaker fixed contact, and wherein the disconnector unit includes at least a disconnector movable contact which can be actuated, during the operation of the disconnector unit, between a connection position where it is connected to a corresponding disconnector fixed contact and at least a disconnection position where it is disconnected from the corresponding disconnector fixed contact, a casing including a first shell made of insulating material coupled to a second shell made of metal material, said casing housing at least the circuit breaker unit and the associated disconnector unit of said at least an electric phase.
In another exemplary embodiment of the present disclosure an electric apparatus including a switching device such as the switching device defined by the annexed claims and disclosed in the following description, a first operating mechanism operatively connected to and adapted to drive the first actuating means of the switching device to cause the actuation of said at least circuit breaker movable contact of the circuit breaker unit, a second operating mechanism operatively connected to and adapted to drive the second actuating means of the switching device to cause the actuation of said at least a disconnector movable contact of the disconnector unit, interlocking means operatively connected to the first and second operating mechanisms and adapted to avoid (e.g., prevent) the driving of said second actuating means by the second operating mechanism, when said at least a circuit breaker movable contact is in the closed position.
Another exemplary embodiment of the present disclosure provides a switchgear including at least a switching device and/or at least an electric apparatus such as the switching device and the electrical apparatus defined by the annexed claims and disclosed in the following description.
In the following description reference will be made for example to an exemplary electrical switching device, an exemplary electric apparatus and an exemplary switchgear suitable for being used in medium voltage applications, wherein for the purpose of the present disclosure the term “medium voltage” is referred to applications with operating voltages in the range from 1 kV to some tens of kV, e.g., 30 kV or 40 kV.
It is to be set forth that the switching device, the electric apparatus and the switchgear according to the present disclosure can be used in applications having a greater voltage, e.g. in an applications having a voltage greater than 40 kV.